This invention relates to an improved method and apparatus for sealing of filter bags.
Normally, the fluid pervious bag material is wrapped around until the ends of the material overlap each other to form a cylinder. The ends are then sewn or bonded together. Often a mandrel is used to aid in wrapping the material. The open bottom end of this formed cylindrical shaped bag is then cut to form a V-shape and then sewn. However, such stitching lowers the efficiency of the filter bag around the needle holes and increases the likelihood of leakage under high operating pressure.
In some methods of manufacture, a hot blade partially cuts the cylindrical plastic fibrous bag material at the edge of the open bottom to allow the blade to penetrate several inches into the bag. The separated layers of the bag contact the blade and are partially melted. The separated melted layers are pressed together and fused. The bottom of the bag is then cut into a V-shape. The length of the hot blade must be sufficiently long to ensure that all the area of contact between the layers is partially melted to completely seal the bottom. However, the seal is very weak where the bag material is first cut and heated by the hot blade. At these areas, the melted material forming the adhesive which seals the bag is less thick and weaker than the material itself.
This invention improves both the side wall and end wall sealing of the bag.
The invention includes a mandrel having a ridge that creates an opening for the insertion of the hot blade between the overlapping longitudinal ends of bag material composed of micro-woven filaments when the material in sheet form is wrapped around the mandrel. The blade is tapered so that it contacts and heats all of the bag material at the overlapping ends. Protruding needles from the mandrel hold the bag material at the overlapping ends until the ends are clamped and fused together. Two exterior hot blades then enter the open bottom of cylindrical bag and expand outwardly with a wedge shaped hot blade being inserted between them. Pressure bars clamp down and laterally fuse the bottom in a generally V-shaped configuration as the three hot blades are withdrawn. A pair of heat cutters or trimmers cut the bottom of the bag along the V-shaped fusion.
It is an object of this invention to provide an improved mandrel apparatus for sealing the side of a filter bag.
It is another object of this invention to provide a mandrel such that the bag material may be securely wound around it.
It is another object of this invention to provide a blade apparatus that forms a stronger seal on the bottom of a filter bag.
Other objects will become apparent upon a reading of the following description.